Polymer-Dispersed Liquid Crystal Films with Low-Driving Voltage and Fast Response

In recent years, the demand for energy-efficient building technologies using smart windows has been growing due to the ongoing energy crisis. The fabrication of polymer-dispersed liquid crystal (PDLC) films for smart windows requires meeting crucial criteria, such as lower driving voltage, improved contrast, faster response, and reduced relaxation time. In this study, PDLC films were prepared using the polymerization-induced phase separation (PIPS) method, incorporating nematic liquid crystals QYPDLC-421 (LC421), 3-SH thiol monomers (trimethylolpropane tris(3-mercaptopropionate)), cross-linker-1,4-butanediol diacrylate (BDDA), and dopants such as disperse orange 25 (DO25) dye and multiwalled carbon nanotubes (MWCNTs) to enhance the electro-optical and dielectric properties. Scanning electron microscopy (SEM) was employed to study the morphology of LC droplet cavities formed within the cross-linked polymer network. The PDLC film with 3-SH/BDDA (30/10 wt %) exhibits reduced driving voltage, faster response time, and lower relaxation time due to weak anchoring at the LC-polymer interface, which facilitates easier realignment of LC molecules under an applied field. These properties are further improved with the addition of DO25 (0.1 wt %) and a combination of DO25/MWCNTs (0.1/0.05 wt %). The impedance spectroscopy of these films was studied using a precision impedance analyzer over a frequency range of 20 Hz to 20 MHz at room temperature, and an electrical equivalent circuit (EEC) was modeled using the EIS spectrum analyzer software.